August 15, 2003: Above their heads, the afternoon sky is turning dark, even as fog drops like a curtain over the glacier-covered peaks of the mountains and fills the valley of the river flowing toward them. Olga Tutubalina and Sergey Chernomorets walk carefully along the left bank of the river through a mix of boulders, loose rocks, blocks of ice, and boot-sucking black mud that stretches for miles before disappearing into the fog and the folds of the mountains ahead. It’s their fourth trip to the Caucasus Mountains in the southern Russia republic of North Ossetia since October 2002. Today, they hope to finally see up close what so far they had only been able to see from a distance: the starting point of the largest glacial collapse ever recorded.

Avalanche

Running east to west across the narrow isthmus of land
between the Caspian Sea to the east and the Black Sea to the west, the
Caucasus Mountains make a physical barricade between southern Russia to
the north and the countries of Georgia and Azerbaijan to the south. In
their center, a series of 5,000-meter-plus summits (16,000-plus feet)
stretch between two extinct volcanic giants: Mt. Elbrus at the western
limit and Mt. Kazbek at the eastern. Volcanism fuels hot springs that steam
in the alpine air. On the lower slopes, snow disappears in July and returns
again in October. On the summit, winter is permanent. Glaciers cover peaks
and steep-walled basins called cirques. The remote, sparsely
populated area is popular with tourists and backpackers.

One year after the Kolka Glacier collapsed and partially buried the Russian village of Karmadon, a team of researchers set out to explore the region on foot. The team combined satellite imagery with their first-hand knowledge of the area to investigate the causes of the avalanche and evaluate future hazards. In this photograph Sergey Chernomorets (left), Olga Tutubalina (right), and their field assistants pose on a pile of glacial debris. (Photograph courtesy Alexander Aleinikov)

On the evening of September
20, 2002, in a cirque just west of Mt. Kazbek, chunks of rock and hanging glacier on the north face of Mt. Dzhimarai-Khokh tumbled onto the Kolka glacier
below. Kolka shattered, setting off a massive avalanche of ice, snow, and
rocks that poured into the Genaldon River valley. Hurtling downriver nearly
8 miles, the avalanche exploded into the Karmadon Depression, a small bowl
of land between two mountain ridges, and swallowed the village of Nizhniy Karmadon and several other settlements.

Between the Black
and Caspian Seas, the Caucasus Mountains separate Russia (north) from
Georgia (southwest) and Azerbaijan (southeast). Elevations reach 5,642
meters (18,511 feet), and glaciers accumulate from heavy snowfall in the
steep mountain valleys. Around Mount Kazbek, a dormant volcano, glaciers
intermittently collapse, burying the landscape below under rock and ice.
(NASA Image by Jesse Allen and Robert Simmon based on MODIS data)

At the northern end of the depression, the churning mass
of debris reached a choke point: the Gates of Karmadon, the narrow entrance
to a steep-walled gorge. Gigantic blocks of ice and rock jammed into the
narrow slot, and water and mud sluiced through. Trapped by the blockage,
avalanche debris crashed like waves against the mountains and then finally
cemented into a towering dam of dirty ice and rock. At least 125
people were lost beneath the ice.

When the Kolka Glacier
collapsed in September 2002, ice, mud, and rocks partially filled the
Karmadon Depression, destroying much of the village of Karmadon. The
debris swept in through the Genaldon River Valley (lower left) and backed
up at the entrance to a narrow gorge (top center). The debris acted as a
dam, creating lakes upstream. This aerial photograph (looking north) was
taken only 16 days after the disaster. (Photograph courtesy Igor
Galushkin)

Dmitry Petrakov, Sergey Chernomorets, and Olga Tutubalina have been returning to the site since the disaster. The three have been friends and colleagues for several years. Tutubalina and Petrakov are members of the Faculty of Geography at Moscow State University. She teaches and researches in the Laboratory of Aerospace Methods for the Department of Cartography and Geoinformatics, and he is a researcher in the Department of Cryolithology and Glaciology. Chernomorets is the General Director of the University Centre for Engineering Geodynamics and Monitoring in Moscow.

The combination of backgrounds made the team uniquely qualified to study
the Kolka disaster. In the year following the event, they made five trips
to the Russian Republic of Ossetia in the central Caucasus. They wanted to
figure out exactly what had happened that day and to
forecast what might happen in coming weeks, months, and years at the
site.

This pair of satellite images, taken before and after the collapse, shows the vast extent of the disaster. Debris and ice filled the Genaldon Valley from the Kolka Glacier Cirque to the Gates of Karmadon—a distance of about 18 kilometers (11 miles). (Images by Robert Simmon based on ASTER data)